【摘要】 氧是镍基合金中常见的杂质元素，以固溶体和氧化物夹杂的形式存在，其中固溶态的氧对合金性能的影响较低，但以氧化物夹杂形式存在时，通常成为疲劳裂纹的萌生以及扩展通道，影响高温合金的断裂寿命。镍基高温合金DD10母合金中的脱氧元素主要为C, Ta, Cr和Al等。本文通过建立九元共存理论热力学模型，研究了温度、真空度以及合金元素对冶炼初期真空碳氧反应的影响。结果表明，温度为1873 K，真空度为69 Pa时，0.05%C能将氧含量控制在45×10^-6。通过扫描电镜（SEM）和能谱仪（EDS）对DD10母合金铸锭中氧化物夹杂的成分、尺寸等进行统计，总结了冶炼全期夹杂物的演变规律。在冶炼初期，Ta和Cr也起到一定脱氧作用，形成球形的CrTaO₄夹杂物，加入Al和Ti后，在活泼元素Al的置换反应下，夹杂物被改性为Al-Cr-O类夹杂物；随着耐火材料受高温分解作用影响，炉衬向合金液中传Mg，最终夹杂物改性为易上浮的Mg-Al-Cr_少-O类夹杂。根据温度为1873 K镍液中的Al–O反应平衡，当Al含量为0.265%时，溶解氧含量降至0.56×10^-6。结合研究结果，针对DD10母合金中易氧化元素含量高的特性，提出了低氧冶炼工艺。更多还原

【Abstract】 Oxygen, a significant impurity element, is commonly found in nickel-based superalloy DD10 in the form of oxide inclusions and solid solutions. During practical service, oxide inclusions in superalloys can initiate cracks and diminish essential alloy properties such as plasticity, toughness, creep strength, and endurance. Hence, reducing both the dissolved oxygen content and oxide inclusions in the alloy is imperative for ensuring the cleanness of the nickel-based superalloy master alloy. Given the substantial presence of readily oxidizable constituents within nickel-based superalloys, this study referenced Gibbs free energies associated with various alloying elements reacting with one mole of oxygen in a nickel liquid, analysis of the alloy’s deoxidation sequence throughout the complete smelting process was performed using an oxygen potential diagram. Additionally, a nine-element melt coexistence theoretical model for Ni-Ti-Al-Ta-Cr-Mo-Co-W-C was established, and the impact of temperature, vacuum level, and alloy element content on vacuum decarburization was analyzed sequentially. Furthermore, the composition and size of oxide inclusions in master alloy ingots were counted using a scanning electron microscope（SEM） and energy dispersive X-ray spectroscopy（EDS）. The evolution of these inclusions throughout the entire smelting process was summarized by referencing data from the thermodynamic software FactSage 8.2. Furthermore, the equilibrium of the Al-O reaction in the nickel liquid at 1873 K was illustrated employing the Wagner model. The essential quantity of Al required was determined by calculating the minimum balanced oxygen concentration at equilibrium in the model. Subsequently, a comprehensive process for deoxygenation during vacuum induction smelting was meticulously designed. Finally, the accuracy of the model’s computational results was substantiated through smelting DD10 master alloy in a laboratory 2 kg vacuum induction furnace. The findings indicated a discernible deoxidation priority among the alloying elements, delineated as follows: Mg, Al, C, Ti, Ta, Cr, Mo, W, and Ni. Constrained by kinetic and temperature conditions, carbon deoxidation alone can only lower the dissolved oxygen content in the alloy to 50×10^-6. An additional strong deoxidizing element, Al, was required for a secondary, more thorough deoxidation. Based on Al-O equilibrium theory calculations, as Al content increased, the dissolved oxygen content initially rose and then subsequently decreased. At the Al content reached 0.256%, the equilibrium oxygen content reached its theoretical minimum of 0.56×10^-6. In summary, this paper designed a deoxygenation process in DD10 master alloy vacuum induction smelting, which comprised three stages: primary carbon deoxidation, secondary aluminum deoxidation, and aluminum alloying. Initially, the dissolved oxygen content was lowered to 50×10^-6 through carbon deoxidation in the early smelting stage. Subsequently, 0.265% Al was added to further reduce the dissolved oxygen content in the alloy to 0.56×10^-6. Finally, the alloying of Al and other oxidation prone elements occurredin the late smelting stage.更多还原